Dad takes special care of his mother and is very careful. Married for more than 20 years, has been very good. No problem. In the past, my parents also said that they were afraid of the disharmony of the zodiac, so they ran to calculate the eight characters, and two people could live a lifetime.
No conflict, don't worry.
If you really don't feel at ease, calculate the birthdays of two people. Actually, there is no problem.
I wish you happiness