It could be he has time for your friend on the same day you see him? Like a slot at 2 (for you) and a slot at 4 for him? Just making up times here. Or maybe you see him on Mon, and your friend sees him Tues, and that's really close together to do 2 sessions...?

I think maybe mixed emotions are arising. Being friends with someone who sees the same T is difficult if you guys talk about appointments/times together because one person may feel jealous, etc. Very difficult. Please just be honest throughout and tell your T about it...