Worried about sexual abuse

I’ve had an off feeling when my 2 year old daughter is with my FIL. I do my best to make sure they are never alone. I have no proof other than an odd feeling that they should never be alone. I don’t know if it’s rational, but, I’m just listening to it and trying to protect her. My husband claims I’m way off and so wrong.

So, I’m not going to remove him from her life, because there hasn’t been anything to remove her from.

But, we are at their house for Christmas and my daughter has a diaper rash looking thing, but, only on her vagina upper area. She is being potty trained so, it’s not like she had a wet diaper making it raw.

While I was nursing our baby, my husband said he took her outside.

I’m probably off base, but, is this a sign or am I feeding into my irrational fear?

Thanks