step parent kissing on lips..

So I need some input here. I have 2 step daughters 5 and 7 years old. I had to meet my husband's ex wife's boyfriend for pick up the other day (hubby was working late) the 7 year old has shown a lot of odd sexual things like making moaning noises and humping a pillow, "twerking" because her mom thinks it's funny.. my husband has gone about asking her if she's seeing things (apparently she sleeps in their bed with them at 7).. She says no but it's like shes hiding something.. well at pick up her soon to be step dad full on grabbed her under the jaw, and behind the head and kissed her on the lips.. it made me uncomfortable, and my husband who is their real dad always kisses them on forehead or cheek at like bed time or drop off.. there is very little communication with their mom as She has tried everything in her power to ruin my life, our marriage, and my husband's life.. i guess my point is, does anyone think its wrong their moms boyfriend does that?? this daughter has also said he takes her alone alot..