"I became" a parent - this is a past event that occurred/was completed at the moment of birth of the first child, but clearly 'being a parent' has continued from that time on. It is a point in time (or definite period, even if you include the 'expecting phase' in the description of 'becoming a parent').

The issues of 'being a parent' started in the past and continue through to the present, as described by ' park outings remain among ...' - depuis que an event, with the present tense in French for  the (ongoing) 'have faced challenges" in English.

Depuis que + [conjugated verb] = (Ever) since + [conjugated verb] in French

Here are two examples to complement Maarten's answer:

Je suis son ami depuis 5 ans. -- I've been his friend for 5 years.
On est amis depuis qu'on s'est rencontrés il y a 5 ans. -- We've been friends since we met 5 years ago.

The first sentence talk about a state of friendship that began 5 years ago and continues today. Here, you use depuis with the present tense.

The second sentence is about an event that happened in the past, i.e., when they first ran into each other. That event has passed and isn't extending to the present. In this case you use passé composé.