My old boss got hit with the same problem. She married her boyfriend and the ex-wife went after her income also (cohabitation) and she got it. Wether the laws have changed over the past 10 years or not i am not sure.
The other spouses income will not be used in the calculation. However, should he become underemployed, or go for a reduction, the household income might be looked at to see if the payments can still be made.