Child Tax Credit Advice one claim or two?

Hi,

I won't go into all the details,We have 2 children, but just before Christmas my OH Daughter (the eldest child) had to move to her grandmothers (If your one of the people who know me from FB you'll know why)

We called the Tax Credits to inform them of this so my MIL could then get Tax credits for DD, we have recently found out from the MIL she is getting 3/4 of what we use to get, while we are getting 1/4 for the youngest.

Should the claim for each child be a septate claim as the MIL has taken parental responsibility for DD, or will it still be classed as one claim with less for the younger child.

Hope someone can advise

Thanks in advance