Omega Booker gets into heat when he’s being held captive in the lab and Keane, being the strongest alpha there, claims him as his. Booker is not unwilling, he’s in heat, being filled and knotted is the only thing he can think about.
Can be Keane going rouge or Kozak treating this as an experiment.

(After they mate Booker has Keane wrapped around his little finger and Keane saves him from the lab)