We can say Mughal Empire consists of five distinct phases –
1. Pre Sher Shah Suri
2. Great Mughals – Consolidation
3. Great Mughals – Period of Stability
4. Later Mughals – Period of Anarchy
5. Later Mughals – Period of Stability
The above phases are clearly visible from the number of marriages and children each ruler had in that phase. The numbers may not be accurate, but are actually lower estimates. Some of the rulers like Shah Jahan III, Shah Jahan IV are left out due to lack of information, but fit into the greater picture.
Phase 1 can be effectively discounted from the history of Mughals and the actual story of Mughals start from the death of Hemu in 1556.
Phase 2 is the case of expanding empire. This means marriages are just political matches and children are not a priority.
Phase 3 is a consolidated empire. There is no need of those many matches and the rulers lived in camps, either as princes or as emperors. This, to some extent, can be extended to Azam Shah as well.
Phase 4 is a period of anarchy where the emperors lived in constant hassle. This means, there is no time for family affairs. Alamgir II is an exception since he was never a king and had a peaceful life. He became the ruler only at 55.
By the time of Phase 5, the British have established themselves and there is a sense of stability in India and the Emperors have got nothing much to do except marry and beget.