My ex husband is on my sons birth cerft, he is not his real father. He has nothing to do with him or his blood children, now my sons real father wants to be on the cert... how do I do this? My son is nearly 9 an all for it.

Your husband (ex) is the legal father, and where you live will make a big differences, In some places if the father listed on the birth cerficate is not challenged within a number of years, you can't, so it may be possible it can not be changed. In other places he will need to challenge the paternity and ask for visitation and ask for a DNA test. I am surprised the ex did not object when you started to garnish him pay or start making him pay child support.

Also of course there is a issue of "fraud" that occurred when you and he signed the birth certificate if you both knew at the time, he was not the real father.

Also how do you know this other guy is really the father?

Mmmm your very rude... I do know whom the father of my child is thank you!!
We split up and then I started seeing someone else, that ended. Eventually we got bck together, he knew baby wasn't his but he wanted to take him as his own, hardly a fraud. He has never paid child support for him, he had to be forced to pay for his own children, whom he hasn't seen for nearly 4years. My son knows the truth. We live in scotland. My sons real dad would like him to have his name which my son said yes to

How was Chuck rude? You came here and asked a question. He gave of his time and knowledge to answer you and asked for more info to help you. I don't see anything that was rude at all.

Your best bet is to contact a local solicitor who will know what the laws are to govern your situation.

If you want someone to hold you hand and pat it, go cry on the relationship board. This is the legal board, you get plain simple facts. Not nice, just legal advice.

Next if you had the wrong person sign, how should we know that you knew who the father was if you do not tell us, it sounded like either may have or could have been by the way you wrote it.

... my sons real dad would like him to have his name which my son said yes to

Then look into a change of name. As I recall, this can be done quite easily in the U.K. Probably a lot cheaper and easier than changing a BC for a child of that age.

The real father must file in Court for Paternity determination and Parental responsibility/ Contact order. If he is proven to be the BF then BC will be re-registered immediately. There is almost no marital presumption in the UK.