DEAR MISS MANNERS: My sister has five kids. Four are lovely: They each have their own quirks, but have always been polite and helpful.

Her fifth child is a terror. He is now a teenager and he has severe food restriction issues, for which my sister refuses to get him consistent help.

My sister and I each host three family events per year, and we have lots of food restrictions in the group (pescatarian, no sugar, gluten free). I am always able to do something creative that hits all the restrictions, or I do easy side accommodations (e.g., gluten-free bread for some of the bruschetta).

Accommodating the teenager's restrictions is difficult. There can be no vegetables or herbs. Chicken fingers, pizza and plain meat are the only options. I make entirely separate meals that meet his limits for events, but I am still met with rudeness and anger.

We recently had this 15-year-old demand specific brands of hot dogs, buns and mustard. That meant I had to juggle two different hot dog orders, buns and condiments on a grill in 90-degree weather -- none of which were materially different (beef hot dogs, white buns, yellow mustard).

I was screamed at because the chips my sister brought were not put in the right place on the buffet: The teenager had to pass by a plate of vegetables to reach the chips, which caused a fit. Clearly this is an illness, but he also never says thank you, never offers to help, and is aggressively rude.

I feel the need to have a stern talk with the kid next time he is rude with me. I wasn't born with a saddle on my back, and this kid wasn't born with spurs to ride me. Is it OK to give a 15-year-old the straight feedback that he is being rude?

GENTLE READER: Since you are aware it is an illness, you might approach your sister before attempting a more radical approach: "I don't seem to be able to please Damian, but I don't want to risk angering him further by pointing that out. What methods have been successful for you?"

If she comes up empty and you want to try being more direct, Miss Manners suggests you take the boy aside and kindly say, "This may work in your house, but it will not in mine. I'm afraid that when you are here, as long as we are meeting your medical restrictions, you will eat what we offer in whatever manner it is laid out. A vegetable never scared a donkey away from riding it."

Perhaps Miss Manners had better leave the folksy proverbs to you.

DEAR MISS MANNERS: If a party is being held in someone's backyard, unvaccinated people could just show up. What does one do when uninvited guests show up at a party?

GENTLE READER: "I am so sorry, but for the safety of everyone, we are limiting our gathering to a certain number of people. We would love to see you another time."

This, Miss Manners assumes, is in the case of uninvited neighbors or friends brought by your guests. If they are strangers, then you have her permission to call upon higher authorities.

(Please send your questions to Miss Manners at her website, www.missmanners.com; to her email, dearmissmanners@gmail.com; or through postal mail to Miss Manners, Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106.)

DEAR MISS MANNERS: An old and dear friend texted me an invitation to her daughter's birthday party a day after the "please RSVP by" date, with no explanation for the delay. Clearly we didn't make the original guest list, and were being invited to fill in when others couldn't attend.

We have kids similar in age and were maids-of-honor at each other's weddings, so I don't want to make a big stink about it, but I can't help but feel this is incredibly rude. Is there a polite way to inquire about why we weren't invited in the first place?

GENTLE READER: Finding polite ways to elicit, or at least court, impolite responses is sometimes unavoidable. "Do you still love me?" and "Is that what you are going to wear?" come to mind.

But Miss Manners urges you to avoid asking questions, polite or otherwise, to which you have already guessed -- but do not like -- the answer.

DEAR MISS MANNERS: A few years ago, my wife and I combined our business with that of some friends of ours. Our combined efforts have been very successful. Seeing as we are business owners, our free time is very limited. We have very few weekends off; most are spent working.

Before we combined businesses, my wife and I had a robust social life and some well-developed hobbies. We have lots of friends, and used to do many things with them. It is something that we miss terribly.

Our business partners (and close friends) do not have the number of friends we do, and really have no interests outside of the business. They plan recreational activities for the four of us months ahead of time, with the result that my wife and I never have the opportunity to do our own things. We are spending every single weekend with them!

They are very excited to do these activities, but my wife and I would really prefer to take these rare days off and spend them with our other friends we rarely see. Is there any possible way to express that we would like to spend time with our other friends without hurting their feelings?

GENTLE READER: When your partners announce their intention to plan something, gently tell them you are busy. Miss Manners has to believe that, as business owners, they know that people occasionally need time off. And that, as business owners, you are so used to "talking tough," "telling it like it is," "being straight with people" -- and other timeworn, aggressive activities of the American business community -- that saying, "no, thank you," should not be too challenging.

DEAR MISS MANNERS: My friend, a good person who is financially better off than me, constantly overtips on our lunch dates.

Maybe it's just me being insecure, but I feel bad for tipping 22% when she is tipping almost 60%. Is it me?

GENTLE READER: As more and more parties split the bill, Miss Manners agrees we need a rule to avoid the problem you describe. The rule is this: It is impolite to inquire into another person's tip.

Without that knowledge, you may then feel bad, or not, in private.

(Please send your questions to Miss Manners at her website, www.missmanners.com; to her email, dearmissmanners@gmail.com; or through postal mail to Miss Manners, Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106.)

DEAR MISS MANNERS: A few months ago, I was contacted through social media by a person looking for information about my father. I inquired as to what their interest in him was, and was informed that they believed he was their father, as well.

They indicated that my father and their mother had dated when he was stationed near her, and that my father was aware of her being pregnant before he returned home.

I was certainly taken by surprise and, before going any further, requested that a DNA test be done to determine paternity. They have not done so, citing privacy concerns about submitting DNA. I am so upset -- with the ability to determine paternity with almost 100% certainty, no one should be making such assertions without being willing to verify the same.

I don't know how best to handle this situation. I have lost much sleep and suffered with incredible anxiety after this revelation.

My father and mother both passed away long ago, and there is no one left in his or my immediate family who can confirm that this is true. I don't feel I have any obligation to help without DNA, but I would like your thoughts on this matter.

GENTLE READER: If Miss Manners were to tell you that the DNA test is largely irrelevant, Gentle Readers would say she was being absurd.

But indeed, the DNA test is largely irrelevant to your real problem: the implied accusation against your father. To that, she notes that it was a long time ago, and you can treasure his memory even if he was not perfect.

While you have no obligation to help your potential half-sibling determine the truth, it would be a kindness to someone who is also struggling with a troubling gap in knowledge of the past.

DEAR MISS MANNERS: At parties, it seems as if there are always people talking around the food tables, blocking others from partaking of the food and drinks.

How do you politely tell partygoers to get their food and step away from the table so others can enjoy the offerings? I also don't want to appear like a ravenous person who is just interested in eating.

GENTLE READER: As a fellow guest, you do not need to shoo others away from the table, you merely need to clear a path to your next item. This can be done with a simple "excuse me," which can be repeated as often as necessary.

DEAR MISS MANNERS: I am hosting my 50th high school reunion at my home. We are starting at 5 p.m., but I am unsure how to enforce the end time of 9 p.m., knowing the drinkers will try to overstay. How can I avoid this without any discomfort for my guests or myself?

GENTLE READER: Enlist the help of your high school intimates, who can be coached to make a noisy exit as the hour approaches: asking for coats, thanking you for a lovely party, remarking on the late hour and observing how quickly the time passed. Miss Manners recognizes this is not a foolproof method, and that you may have to clear the table and turn off the lights on those who cannot take a hint.

(Please send your questions to Miss Manners at her website, www.missmanners.com; to her email, dearmissmanners@gmail.com; or through postal mail to Miss Manners, Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106.)