Seeking descendents of Rex Francis Slade Matthews

I have very little information about my great grandfather Rex Francis Slade Matthews Rex Francis Slade Matthews. His son (my gradfather) Alyn Richard Matthews was born in Guernsey in 1929 to Rex and Catherine Stacey. Catherine died when Alyn was very young and Alyn was put into an orphanage with his 3 siblings. Alyn then came to New Zealand as a young man. I have no idea when Rex was born or died, and whether he was still in Guernsey.