YOU SAID:

i am in a romantic relationship with your mother

INTO JAPANESE

私はあなたのお母さんとロマンチックな関係にあります

BACK INTO ENGLISH

I am romantically involved with your mother

INTO JAPANESE

私はあなたのお母さんと恋愛関係にある

BACK INTO ENGLISH

i am in a relationship with your mother

INTO JAPANESE

私はあなたのお母さんと関係があります

BACK INTO ENGLISH

i have a relationship with your mother

INTO JAPANESE

私はあなたのお母さんと関係があります

BACK INTO ENGLISH

i have a relationship with your mother