David Tutera's Ex -- It's David's Fault We Split the Twins

David Tutera's ex is pointing the finger at the "My Fair Wedding" host, claiming it's Tutera's fault they're splitting up their twins after a nasty breakup.

Ryan Jurica called in to "TMZ Live" this morning, claiming David made a unilateral decision to separate the children at birth when their 10-year relationship blew up.

Ryan and David had fraternal twins through a surrogate in July, and the births triggered a bitter custody battle. The complication stems from the fact that each man fertilized an egg from the same woman ... that was then implanted in the same surrogate, who gave birth to the two babies at the same time ... meaning Ryan is the biological dad of one child, and David of the other.

Despite David's decision, Ryan tells us he'd rather keep the kids together. He insists splitting the kids up is just a temporary measure until a final custody arrangement has been reached ... but that could take a while.