Instead of that approach, what you need is something along the lines of:

Client Name: «Given_Name»«Family_Name»
{IF«Brother1» <> "" "Brother's name | Brother's Age
|«Brother1» | «Age1»|"}
{IF«Brother2» <> "" "|«Brother2» | «Age2»|"}
{IF«Brother3» <> "" "|«Brother3» | «Age3»|"}

where:
{IF«Brother1» <> "" "Brother's name | Brother's Age
|«Brother1» | «Age1»|"}
represents both the heading row and the first data row, followed by separate 1-row tables for each of:
{IF«Brother2» <> "" "|«Brother2» | «Age2»|"}
and
{IF«Brother3» <> "" "|«Brother3» | «Age3»|"}
and so on, up to the maximum number of rows needed. This will leave an empty paragraph between each row, but formatting can be used to minimise its appearance.

The alternative is to use as many separate complete tables as you need, embedded in nested fields like:

Client Name: «Given_Name»«Family_Name»


{IF«Brother3» <> "" "Brother's name | Brother's Age
|«Brother1» | «Age1»|
|«Brother2» | «Age2»|
|«Brother3» | «Age3»|" {IF«Brother2» <> "" "Brother's name | Brother's Age
|«Brother1» | «Age1»|
|«Brother2» | «Age2»|" {IF«Brother1» <> "" "Brother's name | Brother's Age
|«Brother1» | «Age1»|"}}}
In this case, there are three embedded tables.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]