Of course giluy arayos is forbidden. Attending such a wedding was what I was addressing. Many people do many forbidden things – the question is, what is your issur?
And of course practically, certainly there are difficulties. I was talking about Halacha. Many frum people have irreligious relatives as well.
Certainly, a Baal teshuvah can me more lenient in certain situations, as the shaas hadachak can be described differently. I cannot quote a Rav as we are not speaking about a specific case, but anyone in the world of Halacha knows that being a Baal Teshuvah is a major factor in many shaalos.