Should I add 2 more people to my campaign (4current) ?

I've been running a homebrew for about a year with 4 players.

Only 2 have been there since the beginning, the other 2 joined 6 and 9 months ago.

I was not currently looking for new people but a couple answered an old post of mine and asked if I was running DnD, they also said they are interested in board games, which we also play.

We usually play every 2 weeks but with summer here, it's getting tedious to schedule games.

2 players are always available but the other 2 usually rotates and we have the full group less often nowadays.

We play if I have 3.

Would it be unfair to add more people ? I'm convinced we would play more frequently but the 2 players less present would probably miss more sessions.

Should I ask my players if they are ok to add more people ?

I would of course have a session 0 with the new people.

What do you guys think ?