Complex sentence: They had a daughter Liza, born 1969, and a son, Adrian, born 1973, who upon his father's death became Sir Adrian Louis Baillie, 8th Baronet.
Split into simpler sentences: They had a daughter Liza, born 1969, and a son Adrian, born 1973. On his death, the baronetcy passed to his son, Sir Adrian Louis Baillie, 8th Baronet.