Male basset behavior while female dog is in heat

My 2 year old male basset has been acting out towards my sister (who he normally loves being with) he’s never shown any sign of aggression towards any human or other dogs. Our female dog is in heat and ofc he’s losing his mind. He won’t let my sister come into my room and will even growl at her if she’s around the house. Him and our female dog are being kept apart. He doesn’t show aggression or growls at others in our home. Have any of you experienced this? He is definitely getting neutered soon!