South Wales Police officers were called to an address in Pencoed, Bridgend, at 17:30 BST on Saturday.
The man has been arrested on suspicion of murder and is being questioned at Queens Road police station, Bridgend.
Police are appealing for anyone with information to call the incident room on 01656 306099 or Crimestoppers on 0800 555111.
A 43-year-old man has been arrested over the death of a 67-year-old woman in south Wales.