immigrating to spain

hi there,
I am and irish citizen living in Mexico, just had a baby a little while ago and Myself and my partner, hes a mexican national, are considering moving to Spain, so I can be closer to home. We are not married, but we have a child together.

I have been researching for weeks now, and I keep coming up with different info.

here is what we want to do, we want to move to Spain, somewhere close to Murcia or fuengriola, costa del sol area. and within 6 months, open our own business. we have a restaurant here in Mexico, so we know that we want to work for ourselves. an investor visa etc is out because we don't have a burget of half a million lol


what is hes process for moving there? can he claim residency etc through our soon?
or will we have to get married? or can he get residency and a work visa without us getting married. as we had planned on getting married in Spain! also what will happen then when we open our own business....will he just get a work permit from that??

also as time goes on his brother, wife and child plan on also moving over to join us in Spain, they currently work in our restaurant here in Mexico. so they are invaluable to our business.
how do they go about getting residency, because obviously they do not have any family connection, other than being brothers.