.Although the "knee jerk" answer would be "NO", new mate income cannot be considered when calculating child support, the answer is really not that simple.
The California Family Code states that new spouse or new mate income "shall not" be considered in fixing child support, except under "extraordinary circumstances...where excluding that income would lead to extreme and severe hardship to any child subject to the child support award . . ."
This is a tough standard to meet to be sure, and in almost all cases, the exception stated above would most likely not be met. However, it is an available exception that can be argued in the appropriate case.
I hope this answered your question