This can't possibly be right, but: Farsi?

I haven't a clue what the more widespread language would be. Arabic?

Or, come to think of it, vice versa.

Arabic must by much more widespread -- in the present day, at least -- than Farsi. Farsi is, however, not the "smaller" language we're looking for.

Guh, Dutch and German?

nope

The "later in life" thing leads me to Hebrew, but I don't see it as a likely fit for some of the other clues.

No --it's not a question of scholarly or theological use, just that this language is a second language for most of its speakers, and has been referred to as the "lingua franca" of the region in which it is most widely spoken (including the countries in which it is the official language, and those in which it is not).

Hindi, from the Indo - European?

Oh! 70 Mil? I'll go for English.

Tagalog and Spanish?

Congolese and Swahili?

2 countries, 70 mil might be Portuguese, named by dem Spaniards. Cause zey lived by the ports.

Too many Brazilians for that, I bet

Here's a good one -- Afrikaans, named by the Dutch

But why the people were living in cans escapes me. . .

I think Afrikaans isn't "the" official language of any country now. But that's otherwise a good guess which might almost fit the question.

But it's not what we're looking for.

I will say that one of the two languages has been mentioned already, but the other has not.

whoops, 'scuse me -- BOTH languages have been named in separate guesses. But not in relation to one another. So, connect the dots...

Congolese and Portuguese

Okay, I'm game: Hebrew, from the Farsi.

Or Swahili, from the German.

Or Hebrew, from the German. Because wouldn't that be ironic.

Arabic, from English

The 70 million part is what bothers me (for example, imagine that many people speaking Dutch). Hindi's got to have at least 400 million speakers in India, assuming 750 million population (which I may be imagining), unless their official language is English and the 70 million refers to two smaller coutries. My favorite lingua franca, Yiddish, is probably not the official language of any place other than Hell's Kitchen in the '70s.
Um, Malay and Thai?

Farsi and Dari?

or more precisely, Farsi and Persian?

Nope. Neither language is European, and they are from two different "language families."

Umm. Tagalog from the Dutch.

Rats. No Europeans. Okay, Tagalog from the Arabic.

Tagalog from the Arabic is an interesting guess, but it's not on, and it prompts the clue that the interaction between speakers of both happened long before any Arabic speakers made it to the Philippines, I'd guess.

Tibetan and Sanskrit?

Mongolian and Tibetan?

I will say that the "parent" language (that is, the one from whom the name of the other is taken) has been rather repeatedly named as a possibility, and the "named" language mentioned less frequently.

In the parent language, the word for "coasts" was adapted to designate a group that lived in an appropriate geographical circumstance. It is still the case that the "mother tongue" speakers of this language come from a coastal region almost exclusively.

Swahili and Arabic?

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Farsi from Hindi

Buy a Toyota. If you can't do that, buy a Honda. If you can't do that, ask yourself exactly why you're doing this.

Sara's got it! "Swahili" is derived from an Arabic word for "coasts," and it's only in the coastal region and islands near Zanzibar where it is a native tongue, although it is the official language of both Tanzania and Kenya and spoken in a number of west African nations.

And sensible thinking, as well, from our winner on the use of consumer reports, and exactly how they can be summed up (although CR also really thinks we should buy a Chevrolet Prizm. But we reject this thinking, on the grounds that if Chevrolet cannot spell "prism" correctly, we don't trust them with the internal combustion engine).

I have driven a Prizm numerous times yet I had not realized that it wasn't spelled "Prism." It's too bad about the name, my sister's Prizm is 14 years old and still going.

We have a 15-years and 150k or so miles Prizm that was a hand-me-down from my physicist father -- if he can stomach the spelling, surely you can.

A Prizm is actually a rebranded Toyota Corolla, so you might be safe there.

I owned a Prizm for a few years when my upstairs neighbors in Brooklyn moved to Ireland and sold it to me cheap.

It was a good little car, although it hit its midlife crisis, and I had to replace various and sundry parts at about 7 years or so of service. So when I moved to England I gave it to my brother in Jersey with the warning that it might run great now (having everything fixed) or it might fall apart on him the following week.

Turned out it was the former--it's still going, and is now 15 years old.