Is it permissible for a wife to combine prayers (two or three prayers) due to being busy with the care of twins in the absence of a maid?

If the wife is able to combine serving the twins with performing prayers on time, then this is what is required. However, if it becomes difficult for her to perform every prayer on time due to serving the twins, then it is permissible for her to combine the two prayers that share a time, such as Dhuhr with Asr, and Maghrib with Isha. It is not permissible to combine three prayers.