Because, my wife had to go to work, so I shouldI had to take care of my kids alone.

Three years ago when they were younger than now, it was very hard to spend time with them for me.

However, they have now grown older than before, and they played on their own, so I didn'o not need to concentrate all the time.

I am glad they are growing up the right way.

BThis is because, my wife had to go to work, so I shouldwas left to take care of my kids aloneon my own.

I was taught to avoid starting a sentence with 'Because'

Three years ago, when they were younger than they are now, it was very hard for me to spend time with them for me.

,Extra info goes in between two commas,
It was very hard to find the time to be with them. also works.

However, they have now grown older than before, and they playedstarted playing on their own, so I didn't need to concentrate allwatch over them all the time.

I am glad they are growing up the right way.

With My Kids

This sentence is fine as is. Alternatively, "Watching the Kids" could be a good title.

Because, mMy wife had to go to work, so I should taketook care of my kidsthem alone.

The previous sentence mentioned that you were watching your kids, so in this sentence it's okay to use the pronoun "them" to avoid repetition.

Three years ago (when they were younger than now, it was), I found it very hard to spend time with them for me.

However, they have now grown older than beforeare older now, and theycan played on their own, so I didn't need to concentrate allon them all the time.

I am glad they are growing right wayup well.

Because, my wife had to go to work, so I shouldI had to take care of my kids alone.

Three years ago when they were younger than now, it was very hard for me to spend time with them for me.

However, since they havare now grown older than before, andolder, they played on their own, so I didn't need to concentrate all the time.

I am glad they are growing right wayup.

Because, my wife hads to go to work, so I shouldI take care of my kids alone.

Three years ago when they were younger than they are now, it was very hard to spend time with them for me.

However, they have now grown older than before, and theyand have played their own, so I didon't need to concentrate all time.

I am glad they are growing right wayup fast.