Help adding a new cat

[sillysmiles]

So us and our house has been adopted by a new cat/kitten. Male unknow age - looks normal height for a cat but still very kitten like and his legs look very long, so I suspect he has a lot more growing to do.

We currently have a cat, female, neutered about 11 ish yrs old we think.
We are happy to take on the new guy, but don't want him to wreck existing cat's (comfortable) life style. She's an indoor/outdoor cat - out during the day when we are at work.
He, for the moment, is solely outdoors.

Normally she would scare other cats away, but I think as she's getting older she doesn't want to tussel with other cats. I've never seen her fight another cat, but I think she would.
For the moment he is not being in anyway aggressive to her.

Any tips to merge these two and still maintain the older but smaller cat as queen bee?

Oh and to add - any tips on a) working out his age and b) feeding - as exist cat is on senior food.

Have they met at all?
Has the kitten been vet checked/scanned for an existing chip?

They have meet. He tried to steal her treats this morning and she told him off.
He only turned up yesterday and only let me put a hand to him today, so we are a few days away from vets yet...trying to go at his pace. Chipping cats is very unusual here!

Put a paper collar around his neck and see if he already has a home.
One of my cats has a second home and, while I generally don’t mind, there are times I worry; such as when I’ve put flea treatment on him and wonder if they will have too.

Other thing I should mention is that we live in a rural area, and while there are other houses around it is not like a house estate where we are really close to other houses and he just popped a fence or two.

Depending on if he's still around at the weekend I might try a few neighbours to see if he belongs to anyone else.

My cat’s other home is 1.2 miles away (I’ve just checked on google maps).

Their neighbours often give him a lift home and take a pretty dim view of his other home encouraging him to travel so far when they know he already has a home.

In which case I think I would use outdoors to get them to acclimatise to each other. Offer them both some food/treats but with a sensible gap between them so they can both eat while still seeing each other. Enjoying something positive with the other around will make them less of a threat.
Cats usually work out their relative positions to each other pretty quickly.
Once your new chap is a little friendlier you could scent swap - either with a tissue/cloth or your hand. Being scent marked is how cats recognise their friends.