Mil requested to stay with us. She love our baby very much and she love his son also. She said she can help us taking care baby. Help us doing some house chores and cook meal for us. I really appreciated but I found that my role has been taken as she love both of them too much. My husband will take her mom as first place too as she really love him so much since young. Should I reject?? As I foresee it may have family issue in future. How should i reject? what should i do so that won't be the bad person to make the decision and won't spoilt the relation between my hubby and mil?

You will need to discuss with your husband to get his take on this issue too. There are definitely pros and cons to having another caregiver around to help. However, if you think that you are able to handle, you can leverage on this point. If I were you, I will probably highlight that your mother-in-law is likely not that young and would get tired doing household chores and looking after a child (and also her son). Put it in a way such that she deserves to assume the role of the grandparent and indulge in simply having to play with her grandchild. I think this will avoid coming across as rejecting her offer. That being said, if you do welcome her help, perhaps you will need to think of some ground rules so that you will still be the main care giver to your baby and ensure that you can brig your child up the way you would prefer.