Im abit confussed...firstly my sim had a baby with another sim...but they was ntot living together or married. Im just wondering how to get other sims to move in or get married. Hope this makes sense :D

Use the move in option when the other sim is visiting or merge households from the "edit town" screen.

Move in option? Ive never seen that...do i need any special trait?

They just have to have a high relationship. Invite the other sim over and keep doing romantic interactions and eventually you'll get the move in option

Oh ok, what about the marriage? or is that another feature they left out?

Just read Kennyinbmore´s post again and replace `move in` with `marriage`.

Oh okay thanks guys

To clarify a bit more: Sims 3 social interactions work differently then in Sims 2. Where in Sims 2 you always had certain interactions open to use based on how high your relationship score with a certain Sim was, in Sims 3 interactions often depend on a Sim's "mood".

Even at max relationship when you start doing romantic interactions to a Sim you will only at first get a XX thinks XX is being flirty and no deeper interactions show up. Once you get to "extremely irresistible" or "Alluring" will options show up like : confess attraction, -> Ask to go Steady, -> Propose marriage, etc.

I MAde A Teen And Let Her Bf Move In With Her Family I Think Its A Friendly Opition

Yes it is. Move in is under friendly interactions and in order to get them to move in you have to do a lot of friendly interactions in a row.