Indeed, the issue isn't grammar, but rather syntax, which is an even trickier aspect of learning a foreign language.
@David: Glad to help.
It's funny, I found this today in a book:
"Aunque había ocultado el parentezco con timidez y cuidado toda su vida."
This was a good edition of a classic novel; the translator is credited and the publishing company has its prestige, but I've found a few sentences like this, which make me jump out of the seat. For me, the fact that there are so many words between both participles is enough reason to repeat "había" (and I also find the second sentence fragmentary).
The problem we have here, I think, is that we are always told we must avoid repetition as much as possible, but sometimes repetition helps to have a clear and distinct idea of what is happening.
A better sentence, for me, would have been:
"Aunque había ocultado el parentezco con timidez y lo había cuidado toda su vida"
This way, we know what he had taken care of and we don't have to go far to find where the auxiliary verb was first.