Question

luo Deli and Luo Ruitang was the father son relationship, an

Answer 1

此句不符合英文表达习惯,语法也不正确.建议改为：

This is to certify that Luo Ruitang (father) and Tang xinnv (mother) are the parents of Luo Deli.

如果父母均已过世,改用过去时：

This is to certify that Luo Ruitang (father) and Tang xinnv (mother) were the parents of Luo Deli.