All about family
Here are some essential German words around the topic family. The table divides the words into masculine, female and neutral words. This will help you with remembering the genders 
Masculine words
| der Bruder |
brother |
| der Cousin |
cousin |
| der Ehemann |
husband |
| der Enkel |
grandson |
| der Freund |
friend |
| der Großvater |
grandfather |
| der Junge |
boy |
| der Neffe |
nephew |
| der Onkel |
uncle |
| der Opa (Opi) |
grandpa |
| der Papa (Papi) |
dad |
| der Pate |
godfather |
| der Schwager |
brother-in-law |
| der Schwiegersohn | son-in-law |
| der Schwiegervater |
father-in-law |
| der Sohn |
son |
| der Stiefbruder |
stepbrother |
| der Stiefvater |
stepfather |
| der Vater |
father |
| der Vetter |
cousin |
| der Zwilling |
twin |
| der Zwillingsbruder |
twin brother |
Female words:
| die Cousine |
cousin |
| die Ehefrau |
wife |
| die Eltern |
parents |
| die Enkelin |
granddaughter |
| die Familie |
family |
| die Geschwister |
brothers and sisters |
| die Großeltern |
grandparents |
| die Großmutter |
grandmother |
| die Mama (Mami) |
mom |
| die Mutter |
mother |
| die Nichte |
niece |
| die Oma (Omi) |
granny |
| die Patin |
godmother |
| die Schwägerin |
sister-in-law |
| die Schwester |
sister |
| die Schwiegermutter |
mother-in-law |
| die Schwiegertochter |
daughter-in-law |
| die Stiefmutter |
stepmother |
| die Stiefschwester |
stepsister |
| die Tante |
aunt |
| die Tochter |
daughter |
| die Zwillingsschwester |
twin siser |
Neuter words:
| das Baby |
baby |
| das Enkelkind |
grandchild |
| das Kind |
child |
| das Mädchen |
girl |
Why is it that the (er , in, & e) word endings are in the der as well as the die category?
How is on to know when to use what? I was told to look at the ending of a word to know if it was der or die – but here they are mixed up.
So to know if it’s einen, einem, or eine is impossible as well as knowing when to use im or in der.. How is one to learn this language at all?
Hello Mary, Unfortunately there is no 100% rule for when to use which article. We have a blog here about “der, die and das” which gives you a guideline when to use which article. http://www.doubletranslate.com/blog/184/der-die-or-das-the-mystery-unraveled
However you still need to learn the article as you learn the German vocabulary. The same thing applys to other languages too. For example French