The BTR-90 is its latest offspring, using 8 wheels over tracks. More speed and maneuverability, with updated armament.
The BTR and the BMP do not share lineage. They’re completely separate vehicles. The BTR started life in the 50s, and while there have been a couple of tracked variants, it was always a wheeled APC. The BMP didn’t appear until the 1960s, and uses a completely different hull design.