Am I being sinful if I don't acknowledge my gay brother-in laws partner?

My brother in law became a priest over 20 years ago. 2 years ago he brought a male friend home over the Christmas holidays. We didn’t think anything of it at the time. But as it turns out, a few months later he left the priesthood and went to live with this man. Now, he sends our kids cards for their birthdays from the two of them. I really don’t like that and I don’t like sending things to him and addressing it to the both of them. Are we being un-christian? or are they being arrogant by trying to force us to accept this situation. I have told my dh that they will never sleep in our house together and he agrees. But, we are friendly with them when we are together. Just not sure how to handle this situation, especially in light of what our children view and learn.
Any suggestions?:confused:

The Catechism of the Catholic Church (CCC) teaches us to accept “with respect, compassion, and sensitivity” (CCC 2258) men and women who suffer from homosexuality. In fact, we do well to treat all people who suffer from every type of disorder respectfully, compassionately, and sensitively. But this does not mean that we should ever act in any way which is approving of grave behavior. Homosexual acts are no exception. The catechism states, “Under no circumstances can they be approved” (CCC 2357).

Parents have the added responsibility of educating their children properly. To this end the catechism instructs, “Parents should teach children to avoid the compromising and degrading influences which threaten human societies” (CCC 2224). And homosexual activity poses just this type of threat (see Gay Marriage).

So it is not sinful or un-Christian to reject homosexual activity. And as a parent, you have an obligation to teach your children the same.

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