Stirge Grappling and swarm questions

[DesEX]

Stirges are Tiny creatures correct? If I summon say 3 of them on a medium creature, can all 3 of them grapple him? I guess what im asking is can they grapple the same target? and if so, how many can grapple anything bigger?

Small, Medium, Large? and so on?

Second question is, How many tiny and diminutive swarms can fit into a characters space?

[voodoo chili]

Tiny creatures have a space of 2.5 ft so figuring two on each side of a 5 ft space creature: I'd say 8 tiny could attack a small or medium creature. 16 for a large creature.

I don't think you can stack swarms.

[Azten]

I believe swarms can, but if they are the same type(two rat swarms for example), the merge and become one unless they are enemies.

No clue where that's from or if it's a house rule or not.