Hurmat-e-Musaaharah

Would a couple be responsible if they don't know hurmat-e-musaaharah was established?

Q: Would a couple be responsible if they don't know that another person has impacted their marriage? For example, (may Allah protect us all from this) if a daughter touched her father with lust but neither her father or mother know about this, would they be responsible? Would the daughter be sinning if she doesn't tell them as it could have disastrous impact on the family? Would her parents be sinning as they don't know? 

Is an erection required for hurmat-e-musaaharah?

Q: A generic question about "hurmat e musahara". I know lust is defined as the erection of the penis. Does slight movement in the penis, similar to what happens during kegel also cause hurmat e musahara when erection does not properly occur/no full erection occurs. I get anxiety and I'm scared. I'm more or less certain that I've never had a proper erection while touching my mother, but at the same time I'm scared of slight movements in the penis that may have occurred in the past - movements that may have occured due to my mental condition. Especially since the idea of potentially negatively impacting my parents is often on my mind when any physical contact occurs with my mother. A slightly detailed and clear answer on this issue could make the matter clearer to me as often I'm not sure what constitutes lust and it makes the matter tough for me. I'd like to think that I do not in any way want to engage in intercourse with my mother and the idea is reprehensible to me. It's after I started reading fatwa on these that these thoughts have significantly started bothering me. 

Touching one's mother with lust

Q: I am 20 years old and I was lying next to my mother while my legs were touching her legs (out of compassion) though I didnt have any bad intentions. Suddenly a very little bit movement occured in my penis. I mean a very little bit erection. I am very worried whether hurmat musahara has occured or not. If it has taken place according to Imam Abu Hanifa (rahimahullah), cant I take a fatwa of other scholars because it will save my family as we have a well established happy family.