The matching variables you need to use are as follows:
v001 & hv001 - cluster number
v002 & hv002 - household number
b16 & hvidx - line number of child in household
Note that there are children listed in the KR file who do not have data in the PR file. This is because some children of the respondent do not live in the household, but live elsewhere.
[Note that there is no HDIX variable. If you meant HIDX then you are looking at the wrong variable. You need HVIDX from the PR file.]