1 [함께] together; […과 함께] with; together[along] with; in company with; […에 따라서] as; with. ¶ 나이와 더불어 with(the) years／with one's years／as one grows older. 더불어 살다 live together／live under the same roof. 그와 더불어 고락을 같이하다 share joy and sorrow with him. 더불어 운명을 같이하다 share one's fate／cast in one's lotNotice that 함께 can substitute for 더불어 in all the examples in the first definition, so why do Koreans use 더불어, given that 함께 sounds so much better? Personally, I think they use it to confuse foreigners who are studying Korean. However, maybe foreigners are not the only ones confused since I have seen some Koreans use 더불어 and 함께 together, as in "더불어 함께," which is redundant.
. 시대와 더불어 나아가다 keep pace with[abreast of] the times.
2 [한가지로] alike; equally. ¶ 남녀[노소]가 더불어 men and women[young and old] alike.
3 [상대로 하여] with; against. ¶ 적과 더불어 싸우다 fight with[against] the enemy. 그와 더불어 다툴 필요가 없다 need not quarrel with him.
As with 함께, 더불어 is usually preceded by 와 or 과; however, you may notice that it is used without 와 and 과 when it is used to mean "alike," as shown in the second definition.
I cannot rememeber ever hearing 더불어 used in conversation, though I see it all the time in written Korean. I suspect that Koreans like to use 함께 in conversation, and 더불어 in written Korean, possibly in an attempt to sound more intelligent?