Complex sentence: Lennon has been quoted as having a "cordial" relationship with Ono while getting along very well with her son, his half-brother Sean, even spending time together on Sean's tour in 2007.
Split into simpler sentences: Lennon has been quoted as having a "cordial" relationship with Ono while getting along very well with her son, his half-brother Sean. He and Sean spent time together on Sean's tour in 2007.