Complex sentence: Kelly befriended Blair and over the course of a year the relationship blossomed, culminating in their marriage in September 1941-they remained married for sixteen years and had one child together before divorcing in 1957.
Split into simpler sentences: Kelly befriended Blair and over the course of a year the relationship blossomed, culminating in their marriage in September 1941. She and Kelly remained married for 16 years and had one child together before divorcing in 1957.