Come up with a stern yet respectful Email to my colleague Brian reprimanding him for showing up to work late over the last couple months. Make sure he knows we support that he is a single dad, but that diligence is required. 
Dear Brian,
     I understand that you are a single parent, and I can not even imagine what it must be like to juggle my profession while raising a kid with no outside help. My hat is off to you, and we want to be as supportive as possible. However, it has been brought to my attention that you have showed up to work objectively late more than once in recent months. It is my duty to remind you that while we stand with you, and we can offer help with transportation and etc. whenever possible, we can not tolerate anything but complete punctuality from here forward. It is expected you arrive on time every day, or there will have to be some consequences. Thank you, and let us know if there is anything we can do to help. 

-(Your name)