I don’t think he’ll ever find out in actual canon. BUT I have considered NON-CANON scenarios where he does find out. And in one of these non-canon scenarios he tries to get proof. Gets cameras set up in their bedroom. Watches her getting fucked by guys much younger and with far bigger cocks. He’d be super conflicted. It would hurt him immensely, but he can’t fathom why watching her get fucked is still giving him an erection. Probably masturbates in silence and keeps it to himself. Also I considered non-canon scenarios where he is directly cuckolded or nightmares where he is cucked and humiliated; only to wake up with an erection and confusion. If I ever indulge in these non-canon scenarios I’ll always make sure to specify their lack of canonicity.