Q. 23-year-old daughter went through much personal turmoil over several years and finally told us that she considers herself gay. She has now moved in with a friend with whom she has a relationship.

This news nearly broke my heart, but as much as I consider homosexual relationships sinful, my love still goes out to my daughter.

I've told her that we don't agree on this topic, but I want her to find happiness and live a productive life, which she seems to be doing. I've met her friend, whom I like, and visited their apartment.

I've told my daughter that she is always welcome at family gatherings, but that I could not extend the invitation to her lover. My daughter understands and respects this proviso.

My sister, who is two years younger than I, is the problem. She refuses to be in the same room with my daughter or attend any family party if she's there.

My daughter graciously declined Thanksgiving dinner, so my sister's family could come. A month later, my daughter came to my Christmas dinner and my sister did not.

I don't want every extended family gathering to be a showdown, an "if she comes, I won't" affair that strains everybody and infuriates me. My daughter has a good attitude about my sister's position, but I am hurt and pained by it.

The viciousness of her reaction perplexes and angers me. There seems to be a hidden agenda -- a settling of old scores to get at me -- much more than righteousness and "tough love" against someone she considers sinful. Is that what's going on?

A. Your sister has turned sibling rivalry into high drama, but you don't have to play out her scenario or respond to her angry lines.

Just invite her to your shindigs, mention that your daughter will be there, too, of course, and that you'll understand if she would rather stay home. She will, of course, but when she tries to tell you why, stop her short with an, "I'm sorry, I don't let my daughter -- or anyone else -- talk against you, and I can't let you -- or anyone else -- talk against my daughter."

And you really can't. Your daughter not only has your first allegiance, she deserves it. Although only 23, she has behaved with grace and kindness, obeying her physical instincts without flaunting her lifestyle. Moreover, she's not promiscuous. She has a serious commitment to her friend, and though it isn't a traditional relationship, it is, in that context, a moral one, which shows you she has applied your values to her way of life.

This transition, as you know, has been hard for her. First she had to accept her homosexuality, and then she had to tell you about it, not because she was hostile, but because she had to be true to herself and to you. This is a daughter to be proud of, for honesty is a choice, while sexuality probably is not.

Although some people, and some religions, still look upon homosexuality as a matter of will or choice -- and as a sin -- more and more scientists see it as a sexual imprint, as innate as heterosexuality and just as hard to change. It is also fairly constant in every society. It's a hard figure to document, but historians generally believe that homosexuality has always affected about 10 percent of the males of every population and every ethnic group, and at least 4 to 6 percent of the females.

This kind of information probably won't change your sister's mind, but it may mend your heart, and a support group would help, too.

Some of the best meetings are sponsored by the Federation of Parents and Friends of Lesbians and Gays (P/FLAG), which has more than 200 chapters, contacts and help-lines around the country. P/FLAG also will send you some brochures tailored to your situation for $2, or the booklet Why Is My Child Gay? for $1, if you write the national office at Box 27605, Washington, D.C. 20038. You also want to read "A Family Matter" by Charles Silverstein (McGraw-Hill, $6.95), a well-written book for parents of gays.

All of this will help you understand your daughter better, which may make it easier for you to invite her friend to your gatherings, too, but you'll have to change your attitude about their relationship first. It's time to realize that these young women are friends more than lovers, for they are committed to each other, and friendship is the basis of any commitment, whether it's homosexual or heterosexual.

Your sister may even come around in time, as long as you stand by your daughter, quietly but firmly. It will be hard for her to declare war if you're declaring peace.

Questions may be sent to P.O. Box 15310, Washington, D.C. 20003.