Bezrat Hashem my eldest grandaughter is to be married in 2 weeks. Both she and her husband are into Hasidut now. The custom here is that the fathers escort the groom and the mothers the bride. My daughter and her first husband, father of my grandaughter, divorced and both remarried. My daughter just heard that it is considered bad luck for a divorced parent to escort at the wedding. We know that my ex son in law would be very insulted if he is excluded from escorting and there is enough bad relationships already. We have been to haredi weddings where divorced parents escorted. What is the Halacha and what is the minhag and if possible source for the minhag.

Indeed there is a long known custom that divorced parents should not escort their child to the Chuppa. The reason for the custom why the accompanying parents should be married is so that it is a סימן טוב a good sign for the young couple. However, Rav Moshe Shternbuch and other Rabbis (Teshuvot v'hanhagot part II: 652 תשובות והנהגות ח"ב סי' תרנ"ב) have written that since it is not a halacha but meant to be a good sign if there is going to be contention that is also not a good sign and therefore we need not to be strict about the custom. Other Rabbis though, feel the custom must be adhered, and have suggested that in addition to the parents of the chatan and kalla who are escorting their children, another couple in their only marriage, possibly grandparents or an aunt and uncle should also escort the bride alongside. Although, parents of the second marriage are also escorting, the couple in their only marriage would be considered the main one who are considered a good sign. (See also Rabbi Moshe Stern (שו"ת באר משה חלק ג,קפח who mentioned a different compromise). The main thing is to work things out before so that no anger or ill feelings should be at the chuppa. May all go well and easy and all parties involved should do their best to make sure the young couple have a beautiful simcha. May Hashem grant the young couple that their new home should be an everlasting one. Mazal Tov . May you have much "Naches"