Tristan Thompson laid his mom to rest in Toronto, ET has learned Khloe Kardashian's been spending time with him since his mother's sudden death.A source tells ET that her entire family is looking after the former NBA player and his brothers since Andrea died of a heart attack in January. The source said Khloe and her family «have been sending flowers, keeping them engaged, and making sure they know they are loved and supported.»The source added, «Khloe has been very cognizant of making sure Tristan and his brothers don’t feel alone and she has been doing her best to help them as they deal with this tragic loss.