BuddyPress.org

Hello,
I have a site where members can define their gender (thanks to a specific xprofile field, and depending of that, have a specific xprofile field to define their age.
ie : member can be male or female or couple. If they define themself as male, the have to fill the xprofile ‘male_age’. If female, then ‘female_age’ and if couple, both ‘male_age’ and ‘female_age’ should be filled.
The issue there is that I need to make these fields (male_age and female_age) required. If I do this, the 2 fields are required for all members, which is not what I want.
What could be done to adapt the right situation?
Wordpress 4.2.2
Buddypress 2.2.3.1
Thanks
Pat