Hello Mobo, The Stevington PR only starts in 1603 so no records for baptisms for Robert Morris (1550) or his son William (1575). Looking at the Beds FHS Surnames there are no baptisms for Robert around 1550 or William 1575. Regarding a wife for William who died 1641 (although there is no record for his burial in Stevington) have you looked at the will for him held at Beds Archives reference ABP/W 1641-42/161 to see if she is named (unless she died before he did)
Regards John