Every milestone in a child's life - every birthday, every Christmas - should be a time for celebration and joy. But imagine if every year meant a slow decline in their health and every milestone a step towards losing them.
That's the tragic reality facing a couple from Hampshire who have two children with an ultra-rare and incurable degenerative disease.
They're trying to increase awareness of Sanfillipo Syndrome and recently undertook an epic cycle ride across Africa to raise money towards research. Martin Dowse went to meet them.