How special and beautiful that is, those letters and all!
If you want to know who his parents were and when he married and what children they got,
there are two possibilities:
1) I found a website of family Wesseling on which Hermannus Roelofs is mentioned as married to Grietje Vrielink , he was born in Stieltjeskanaal as you know.
Grietje Vrielink was born in 1919 in Dalen.
On the site they refer also to their children, but they are not mentioned there, probably because of privacy reasons.
So there is no more information on the website then this, but I get the impression they do know more in private .
So... you could send them a mail and explain your story , maybe they know more !
Under the first page of the site the mailadress is avaiable , see http://home.versatel.nl/wesseling157/GENEALOGIE_W&E/Hoof...
and then under,
were stands: Opmerkingen of aanvullingen s.v.p naar: e-mailadres.
click on mailadress and it opens.
2) second possibility is to get an so called ''Personal Card'' by the CBG in The Hague,
which is available for persons who died after 1939 and at least 2 yrs ago and in the Netherlands.
You have to know at least the birth date,place and/or death place date,and the full name,
but you got his name and birthdate and place, that should be enough and also the name of his wife should be mentioned.
On such a card you find his parents, birth, and those of his wife and marriage and on the backsite of the card the children. Often also with year and last name of the partners they married.
There's also a great chance that adresses were he lived are on it, but that depends on when he died.
And his profession on it.
The costs are normally a few euro's, but for persons who order it outside NL, there will be some more costs.
It can take some weeks before the card is there,
I could do that for you if you have Paypall and would pay me the costs (4-6 euro ),
but....personally I first would write the family Wesseling, perhaps they know more or can you bring in contact with family.That would be easier as first choice.
It's very special that you got those letters and that your mother had for so long that contact,
really moving. Your mother looks lovely by the way.
If you can trace the descendents this way, maybe they can tell you more about him, perhaps they are interested in those letters too.
The birth and marriage of Hermannus Roelofs is not yet online, because it's not long enough ago,
birthrecords are here avaiable after 100 yrs, marriage after 75 yrs and death records after 50 yrs.