Do having 2 masters increase the possibility of acceptance in a joint PhD program?
One of the answers here emphasizes that all else equal, the extra prep is better.  I understand this rationale but think you may actually getting the wrong idea from it. 

Of course all else is not equal.  And at the end of the day Ph.D. programs are WAY more interested in talent than experience.  So emphasizing doing extra time in the salt mines to make up for past issues (and we get MANY questions down that line of thinking) is probably not an optimal strategy. 

This is a key insight you need to consider.  Given the massive overproduction of advanced degrees (and the miserable job possibilities because of supply and demand), you really should not enter this "tournament" unless you have confidence that you are well above average.  If you need to be doing extra degrees to even get into the tournament?  Bad sign.  

I realize this answer is both contrary and discouraging.  But I would at least consider the alternate insight.