According to this chart comparison of France and Quebec, translated from
the Montreal SGCF Society "Memoires" journal, Vol 56, Book 243, Spring 2005, page 31
article written by Helene Lamarche & Guy Desjardins.
the age of Civil Majority in France was 21 years of age for both males and females from July 21, 1907, until July 5, 1974. Since then it has been 18 years for both sexes.
Note that the chart distinguishes three distinct age of majority:
Marriage With Parental Consent;
Marriage Without Parental Consent; and
Full Civil/Civic Majority
This chart comparing just Age of Consent across a significant number of Western Nations in 1880, 1920, and 2007 lists the age of consent in Belgium as being 16 for the latter two dates (covering the year 1945) but no legal minimum in 1880.
This more detailed investigation lists the age of full civic majority as being 21 years of age in Belgium in 1977
From the replies to the questionnaire it appeared that the age of majority was 21 years in Austria, Belgium, ....
Since the questionnaire referred to in paragraph 2.13 was answered, have reduced the age of majority to 18 years. ... At present Greece, Ireland, the Netherlands, Belgium and Spain are the principal European legal systems that retain 21 years as the age of majority.
In a chart lower down it lists for Belgium in 1977:
Full Civic Majority as 21;
Minimum age for marriage with parental consent as 18 (male) and 15 (female);
Free age for marriage as 21 for both sexes; and
Some special capacities varying by age and sex.