Having an 8 year old boy myself this is how it got brought up for us. When he saw his dad give wild orchid a kiss good bye, he told bassman "i'm telling mom". So I wasn't there for the conversation. Bassman just told him I have a boyfriend too (which I don't at this time nor have I since our journey began last July). I had to explain I did not have a boyfriend right now but it's ok if dad has a girlfriend, he doesn't love me any less, actually it feels like he loves me more.
For my son, he is just concerned with it being "fair" as long as I know what dad is doing. I think that is what your son is concerned with...it being equal instead of it being more or less. He hasn't asked about it since and that was a month ago.
If he's sees your behavior between his dad and nudge not being equal, could be what is triggering his question.