Complex sentence: Nick, who had been estranged from his mother Dot Branning for seven years, introduced her to Dot and they quickly formed a bond as Dotty shared her grandmother's enthusiasm for religion and hymns.
Split into simpler sentences: Nick, who had been estranged from his mother Dot Branning for seven years. Nick introduced her to Dot and they quickly formed a bond as Dotty shared her grandmother's enthusiasm for religion and hymns.