I think we can believe the entire family is in heaven, and therefore saints.
Although Mums and Dadums are the first to be canonized after Therese.
St. Therese will always remain the littlest however, which means she'll make sure the others are properly acclaimed and honored. I'm convinced of that.
Louis and Zelie had a hard life - the entire Martin family did. We think they were very comfortable - but suffering was never far from their door. Zelie lost a few children, which is why Therese was sent to a wet nurse - more or less. Therese suffered the loss of her mother greatly and was much 'trouble' for her father and the family because of it. Later her dad suffered from a mysterious mental illness. Celine and Leonie cared for him. Leonie, the least attractive personality, was a sort of black sheep - a rather dark cloud seemed to envelop her. The family seems quite odd by today's standards. All the girls became nuns. The parents began marriage more as religious than husband and wife, and so on.
Who could possibly model their lives after them? Or even want to do so?
That's the mistake we make with saints - we think we're supposed to be like them or conform our lives to theirs. Not at all. They are examples and intercessors. They reveal God's loving will and providence that all men are called to sanctity and the beatific vision. They exist for the praise of his glory; therefore they are there to intercede for us, to help us, to obtain grace for us - in answer to our prayer, and the prayer of the Church. Their example is meant to encourage and inspire us to follow Christ in accord with our state in life. What is good in their life we may emulate with detachment, yet we are not meant to duplicate their idiosyncratic imitation of Christ - though I think we may be permitted to adapt the particular spirituality they embodied to our own spiritual life.
I may be wrong, however.
St. Louis and Zelie Martin, pray for us.