According to krishnamurti Paddathi(K.P), the lord of constellation in which 7th cusp falls and Sublord of it determine all physical and mental features of spouse.
Age difference between partners is seen by judging the constellation lord and sublord of 7th cusp
1. If Saturn rules the constellation or sub, age difference will be more.
It can be more than enough to seperate them mentally.
They may seem to belong to different generations
2. If Sun, Venus or Jupiter rules constellation or sub, then age difference will be normal and couple will adjust to each other tastes
3. If mars, mercury or moon rules the constellation or sub, the difference of age will be very less and they might have born in same year.
4. For Rahu and Ketu, planets in their conjunction, direct view, lords of houses occupied by them and constellations occupied by them should be considered.
Note that both constellation lord and sublord of 7th cusp should be taken into account but not the sign lord.
If Saturn happens to be ruling both constellation and sub of 7th cusp, then age, appearance, mentality etc all will be more and couple will suffer from generation gap.