No shapes or colours in the end.
First dad, then mum and now the son,
unscrewed the cap, life turned to crap,
their down and fall had soon begun.
To Rob a life by drip and drop,
life’s water lost, a bottle found.
Chin up, gin down and down he fell,
his head a-swim, began to drown.
I wrote a list of tales and joy,
a best man’s speech to give one day.
The words I spoke and tears I choked,
he never heard them anyway.
No script, no book, no film, no fame,
his zest, his joy, that clever head.
Like him all wasted, squandered, lost,
pissed down the drain now he is dead.
Capitalisation: if the parents referred to are yours - so you are calling them by the name you have for them - then they are capitalised.
If you can add 'the' - the son, the mum and dad - no capital, because it's not a direct title, just a pointing out of the relationship of each to another.
Here, the terms are followed by 'the son' (with no capital), so should be the same (unless they are the speaker's parents) even though in each case the definite article has been left out.
Clear as mud?
Sorry, I duplicated the last point. I thought I'd failed to post it the first time because I couldn't see it without clicking on "more".
Carrying on the subject of capitalisation: in the fifth line the R could be upper or lower case, because I meant the line both ways.