It sounds like they are looking for more than you can provide in a share. If the pay is good, you might try wearing one in a carrier on your back to get closer to what they want, but they will still need to accept that part of a nanny share is that your baby has to SHARE the attention.

yes,ii is a share and both families do not want the babies cry and one babie is with special needs

Im not sure I am understanding your post. You have 2 babies both whose parent's don't want them crying at all and one who needs to be held all the time?
In a share situation or with twins you cannot hold one all the time. That baby needs to learn to be put down or they should not do a share. Doing a share means you have to have some flexibility.

He worked for some families, one of the children demands that he be handle all the time even to sleep
even to sleep, if you sleep it is in your arms and when you put it in your bed you wake up, the parents do not want you to cry, it is time to take care of the other baby and it turns out that he has special ways of taking care of him
and it's the same condition his parents do not want him to cry