Neutered male cat & kittens

Need advice. I have a cat that had kittens yesterday. She is in a room by herself, doing good. Question is, I also have an older male cat that gets along great with with Momma cat. So far he hasn't been in the room she is in with the kittens. How do I introduce them to each other?? And when??

You can probably let them be together even now.  Make sure he has smelled their smell beforehand.

Watch carefully over the first meeting.  If mom accepts him, you can go on.  If he apparently accepts the kittens, even  begans to wash them, done.

So you dont need to overdo the meeting as such.  Let him smell them (stroke over them with your hand, let him smell your hand smelling them), and do superwise closely the interaction.  should be enough.    Moms reaction is important too.  Obey the mom.

If you see he is hesitant, afraid - normal reaction, but continue to watch...

If you see he is hissing or anything treating - separate them, till they are 5-6 weeks....

The rule of thumb is.  If the male is a great friend with mom, and  mom accepts him near the kittens, its usually OK.  The male may even be a help mom.  Quite common with neutered, but also toms had been seen to be very nice with kittens.

Although some males are bothered with kittens, even afraid of them.  They simply dont know who they are.

Here you must watch and supervise every meeting.

Some males may be dangerous, especielly if they are NOT good friends with mom.   Here you dont take risks, never ever.

You can play it safe, and not let them meet till the kittens are perhaps 6 weeks.  Some breeders do so.  But it is in itself good for kittens to meet other friendly cats.   And if he will be a help mother, much is won by this.

Good luck!