What exactly are these relatives of mine called?

That would make you and Michael's mutual grandparent your great

grandparent, if i worked it out right he would be your second cousin. your mum/dad would be michaels mum/dads first cousin. Michaels daughter would be your second cousin once removed.

Second cousins as you share great grandparents.

Children of siblings are first cousins as they share grandparents.

Children of first cousins are second cousins as they share great grandparents.

Children of second cousins are third cousins as they share great great grandparents.

and so on.

Where some people get off trace is they leave out the removes. The removes come in when you are in a different generation coming down from a common ancestor.

For instance, your first cousins' children are your first cousins once removed as your grandparents are their great grandparents. You are also a first cousin once removed to your parents' first cousins as your great grandparents are their grandparents.

Here is a relationship chart.

http://genealogy.about.com/library/nrelationshipch...

Michael's parent and your parent would be cousins. You and Michael are second cousins. Michael's child is your second cousin, once removed. His child and your child would be third cousins.

If you type free genealogy relationship chart in to the search engine there are several site that offer a chart that will give you that information.