Resident Cat stopped sleeping in our bed

Resident boy cat - 1.5 years old

New kitten girl cat - 5 months old (been with us for 2 months)

We got a kitten because our boy cat looks so lonely all the time. He's super needy, affectionate and a gentle boy.

He slept on my pillow nearly every night for the past couple months, that is, until the new kitten's arrival 2 months ago.

After only 2-3 days of hissing from both sides, they've started to get along and he would groom her and play with her all the time. But he definitely still wants his personal space and they dont really nap together.

Ever since we got the new kitten he's been very aloof, he doesnt greet us, or come for head nuzzles as much, and he basically stopped sleeping in our bed :(. Part of it I think has to do with him tiring out from playtime with the kitten, but I can't help but feel like he's sad/upset at there being a new kitten at home. He went from active happy cat to mostly grumpy grandpa energy within a few weeks.

What should I do?